1. Field of the Invention
The present invention relates to an ophthalmic apparatus, and more particularly, relates to an ophthalmic apparatus having a measuring part for examining and measuring an eye to be examined and moves the measuring part with respect to the eye to have a predetermined positional relationship therebetween.
2. Description of Related Art
An ophthalmic apparatus, such as an eye refractive power measuring apparatus or a noncontact type tonometer, measures an eye to be examined by moving a measuring optical system provided in the apparatus so as to make a predetermined alignment with respect to the eye. In one alignment mechanism which has been suggested, alignment target images formed by projecting alignment targets on a cornea of the eye are detected and based on information detected thereby, moving means for moving the apparatus is driven and controlled so as to automatically adjust or maintain the alignment. To drive and control the apparatus, the alignment target image being a luminance point is formed on a corneal vertex by projecting an alignment target light from the front of the eye, or a corneal center is detected based on a positional relationship among luminance points formed on the cornea by projecting a plurality of alignment target light thereto.
However, influenced by conditions of a corneal surface, light producing objects (a fluorescent and the like) and tears of an examinee, scattered light may appear as a lot of luminance points on the corneal surface. The luminance points may not be distinguished from alignment target images, which is likely to interfere with a corneal center detection. In such cases mentioned above, alignment conditions may be wrongly judged or may not be detected at all.
As for an alignment mechanism which stores information about luminance points in sequence, if many luminance points are detected due to scattered light, the detection may stop halfway though it because of exhaustion of available memory.